ultrasound

so I had an ultrasound because I was spoting on sat, and my HCG were at 441 on Friday, then sat is when I went to the ER due to spotting but it was just that one time and it was super light but I got scared. then they told me that my HCG were at 449 on sat and they wanted me to go again on Monday ans they went up to 701 and tomorrow I have to go again to get checked. I had an ultrasound but they were not able to see anything no baby they said maybe because I'm too early.I'm kind of scared that they told me they didn't see anything. I'm hoping and praying is because I'm too early. has this happened to anyone?